A function that expresses the ability of an optical or electronic device to transfer signals faithfully as a function of the spatial or temporal frequency of the signal is commonly known as a modulation transfer function (MTF). The MTF is the ratio of the percentage modulation of a sinusoidal signal leaving to that entering the device over the range of frequencies of interest.
In the past, measurement of the MTF for a microscope or lens has typically involved analyzing a wedge (similar to four squares of a checkerboard) at a single location within an image plane. In optical systems including a plurality of devices cascaded in series (e.g., as in video microscopy), the MTFs of the component devices were evaluated separately. The overall MTF of the system was given by the product of the MTFs of the component devices.
However, there have been a number of drawbacks associated with such conventional methods and arrangements for evaluating the MTF of a device or system. For example, it has been found that the MTF measurement of a device based on a single wedge does not sufficiently reflect the integrity of the device, particularly in many high resolution applications. Furthermore, it has been burdensome to obtain separately the MTF of each component device in the system. This required physically separating the components of the system, thereby resulting in system down time. In addition, extended delays could occur as each component device was evaluated separately.
In view of the aforementioned shortcomings associated with conventional MTF analyses and arrangements, there has been a strong need in the art for an improved system and method for analyzing MTFs for one or more optical or electrical devices. In particular, there is a strong need for a system which evaluates the MTF measurements for a device globally rather than at a localized point. Moreover, there is a strong need for an arrangement whereby the MTF of the system can be evaluated in situ and in real time.